For several months, the Republican Senate primary in North Carolina has been a race for second place : state Speaker Thom Tillis, with his superior financial resources, is a shoo-in for first, while Dr. Greg Brannon and Pastor Mark Harris vied for second place to challenge Tillis in a runoff.

But, one week before the primary, many local operatives now expect Tillis will reach the 40 percent threshold on Tuesday to avoid a runoff later this summer with the second-place finisher.

The winner of the primary will face Sen. Kay Hagan, D-N.C., in one of the cycle's marquee competitive contests. For Tillis, the stakes to avoid a runoff are high because it would force him to spend another two months running against a Republican opponent — instead of Hagan.

What's more, the state's General Assembly comes back into session on May 14, eight days after the primary. Tillis would have to balance his duties as speaker while still campaigning for the nomination.

But, many local Republicans now see that scenario as increasingly unlikely, arguing that Tillis will most likely win the primary outright.

“About two weeks ago, I would’ve said we would definitely see a primary runoff,” said Chad Adams, the director of Priorities NC, an advocacy group focused on promoting limited government, who is not aligned with any campaign. “But looking at the landscape now and how we’re shaping up, it looks like that gap is closing.” Adams predicted that Tillis could get to 40 percent, and if he falls short, it will only be by a hair.

“To me, it just feels like, on the ground, that the momentum really shifted recently for Tillis,” one North Carolina Republican strategist not aligned with any campaign told CQ Roll Call.

“I think it’s pretty much a done deal,” echoed a second unaligned North Carolina GOP strategist, who also requested anonymity to speak candidly about the race.

Not everyone is so sure. Turnout in primary races often is low and unpredictable. Tillis boasts a strong get-out-the-vote operation, but both Brannon and Harris have devoted followings within the state.

“We feel good about where we are, but we’re not overconfident,” Tillis campaign manager Jordan Shaw said. “Obviously we’re hoping we get to 40 [percent] ... but we’re prepared for any outcome."

Democrats prefer Tillis face a runoff, but even some Tar Heel Democratic operatives have also come to the conclusion that Tillis will probably wrap it up next week.

Democratic and, privately, Republican operatives give the Tillis campaign little credit for that presumptive accomplishment. Instead, they chalk up his improved standing to the inadequate campaigns of his opponents.

They also cite the influence of outside groups like American Crossroads, which came in at the beginning of April with a four-week, $1.6 million ad buy to boost Tillis. The ad buy ended on Monday, and then the U.S. Chamber of Commerce made a substantial buy supporting Tillis that started on Tuesday.

Without American Crossroads, Jackson said, Tillis would be heading for a runoff.

The volume of Tillis' financial resources, combined with money spent by outside groups on his behalf, has dwarfed his opponents, giving Tillis an advantage. Outside groups could have helped even the playing field for Brannon and Harris, but none have spent significant money to do so yet.

Some North Carolina Republicans had expected Harris to surge in the final weeks of the race, potentially holding Tillis to less than 40 percent. But that's not the case, according to recent polling.

Public polling has shown Harris in third place for most of the campaign: Threepollsreleased in the past week have Harris behind Brannon and Tillis.

A large advertisement buy from Senate Majority PAC has served as a wildcard in the race. One of the Democratic super PAC's spot attacks Tillis for a scandal in which two of his former staffers were found to have improper relationships with lobbyists. One of those staffers was his chief of staff, who shared an apartment with Tillis. The staffers were forced to resign, but Tillis gave them severance packages.

The ad is particularly potent, and could cause problems for Tillis, especially in a general election. But Republican primary voters’ intense dislike of Hagan and the Democrats behind the ad could yield the opposite effect: Rallying voters behind Tillis.

“Harry Reid attacking him on Obamacare is not gonna hurt in a Republican primary,” North Carolina GOP strategist Carter Wrenn said, referring to another Senate Majority PAC ad that attacks Tillis on Obamacare.

Republicans could even "revolt against Democrats meddling in their primary" and decide to vote for Tillis as Hagan's most formidable foe, said Democratic pollster Tom Jensen of Public Policy Polling.

Harris’ campaign is not conceding yet.

“We’re closing it just as strong as any campaign in the race if not stronger,” said Harris campaign spokesman Mike Rusher, pointing to $400,000 cash on hand to spend on media in the final days of the race, and noting Harris’ rise in public polling.

The Brannon campaign did not respond to calls and emails seeking comment.

The race is rated Tilts Democratic by the Rothenberg Political Report/Roll Call.

Correction 3:45 p.m. An earlier version of this post misstated how much American Crossroads has spent to assist Thom Tillis.